Aaron Spelling & Danny Thomas had launched two Westerns in 1967. Rango, with Tim Conway, was a flop, but The Guns of Will Sonnett, with Walter Brennan, returned for a 2nd season, now joined by a contemporary crime drama, The Mod Squad.
A precursor to the 1990's version of 21 Jump Street, Mod Squad put together a trio of socially disenfranchised young people as undercover detectives. Pete Cochran (Michael Cole, no relation to the WWE announcer) came from a wealthy family that seemingly disowned him. Lincoln Hayes (Clarence Williams III) was involved in the infamous Watts Riots. Julie Barnes (Peggy Lipton) was a flower child whose mother was a prostitute. Banded together by police captain Adam Greer (Tige Andrews), they got into places the cops couldn't to get the goods on the bad guys. The series lasted 5 seasons (1968-73), perhaps ending a wee bit too soon, in this writer's opinion.
Mod Squad also ended up being the last hit series Spelling & Thomas developed together. 2 years later, with Squad entering its 3rd season, the two parted ways, with Thomas reviving his earlier series as Make Room For Granddaddy, while Spelling teamed with Screen Gems to produce The Young Rebels, and, on his own, launched his first two entries, Silent Force & The Most Deadly Game. All four series were cancelled after 1 season.
Here's the intro everyone knows, with Earle Hagen's kickin' score:
Me-TV holds the rights to the series currently. Catch it if you can.